A gas meter device detects a change in flow rate of a fluid in a fluid piping system to determine an appliance that uses the fluid (for example, PTL 1 and PTL 2). Gas appliances include fan heaters, gas tables, water heaters, floor heating systems, and the like. Since a characteristic of a change in flow rate of gas upon ignition or the like differs in each gas appliance, a gas appliance being used can be determined by recognizing the characteristic of the change in flow rate. PTL 3 discloses a device for monitoring, by measuring pressure in a gas pipe, whether gas pressure is normal or abnormal.